Is there any other way to access open forms in C#?

Question

 Application.OpenForms["formname"];

Is there any other way to access an open form. My application doesn't see this form although it is opened. I dont know why.

Is this "formname" is the name of the instance of the open form or is it the name of the class of the open form? Perhaps you could post your code here too, especially the one related to "formname" — Ian, Jan 27 '16 at 08:28
Have a look at all open forms: `MessageBox.Show(String.Join(Environment.NewLine, Application.OpenForms.OfType
().Select(form => form.Name)));` can you find the required form? — Dmitry Bychenko, Jan 27 '16 at 08:31
Don't lose track of the form object you created. [Or work around the bug](http://stackoverflow.com/a/3751748/17034). — Hans Passant, Jan 27 '16 at 08:48

score 2 · Answer 1 · edited May 23 '17 at 11:59

I recommend you to firstly debug your code to check what is the Form actual name which you want to load:

foreach (Form form in Application.OpenForms) {
    string name = form.Name; //check out this name!!
    //print, or anything else will do, you only want to get the name
    //note that you should be able to get any form as long as you get its name correct
}

And then, once you know what is wrong with your code, simply do:

Form form = Application.OpenForms[name]; //use the same name as whatever is available according to your debug

To get your form.

To check more on the possible bugs, See Hans Passant's Post

score 2 · Accepted Answer · edited May 23 '17 at 12:31

2

Isn't really necessary a name to get an open form. You can get the form you want by index:

Form frm = Application.OpenForms[0] //Will get the main form
Form frm = Application.OpenForms[1] //Will get the first child

Forms in the OpenForms collection are ordered in the same way that you create it

Otherwise, an alternative is to save a reference to the form and then accessing it by this reference.

//Where you want to save the reference:
Form theForm;
//Where you create the form:
myClass.theForm = new MyForm();
//Where you want to get that form:
MessageBox.Show(myClass.theForm.Caption);

(myClass is the class that will hold your reference to the form, supposing you are accessing it from different classes)

(Also, see if you are affected by this: Application.OpenForms.Count = 0 always)

edited May 23 '17 at 12:31

Community

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answered Jan 27 '16 at 10:36

fruggiero

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*Forms in the OpenForms collection are ordered in the same way that you create it* Is this documented? – nawfal May 12 '20 at 04:43
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@nawfal as we can see from the source: https://referencesource.microsoft.com/#System.Windows.Forms/winforms/Managed/System/WinForms/Form.cs,4833 a form is added to that collection on the form OnLoad event (with OpenFormsInternalAdd). So the order should be guaranteed as long as we show forms in a sequential manner. – fruggiero May 12 '20 at 08:26

score 1 · Answer 3 · answered Jan 27 '16 at 08:34

1

You have to instanciate first a Form. after that you have access to it:

Form1 formname = new Form1();
Application.Run(formname);

// access to form by formname.yourproperty

answered Jan 27 '16 at 08:34

M. Schena

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What does it mean? Application.Run(formname)? – nrtn93 Jan 27 '16 at 11:30
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Begins running a standard application message loop on the current thread, and makes the specified form visible: https://msdn.microsoft.com/en-us/library/ms157902(v=vs.110).aspx – M. Schena Jan 27 '16 at 11:46

Shaharyar · Answer 4 · 2016-01-27T08:44:16.983

0

To access the form using this property your form must have a Name.

Remember its not the instance name nor the the form Text:

  Form1 f1 = new Form1();    //not "f1" is the "Name"  
  f1.Text = "it is title of the form"; //neither "Text" is the "Name"
  f1.Name= "its the name"; //it is the "Name"

Sample:

frm_myform form1 = new frm_myform(); 
frm_myform.Name = "form1";

edited Jan 27 '16 at 08:44

answered Jan 27 '16 at 08:32

Shaharyar

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I know, it is not the text. I use the form name but Application.openForms returns neither null nor something else. – nrtn93 Jan 27 '16 at 08:35
frm_myform form1=new frm_myform(); – nrtn93 Jan 27 '16 at 08:41
Then you can access the form through your `form1` variable, right? – CompuChip Jan 27 '16 at 08:41
Yes. I access it using form1 variable. – nrtn93 Jan 27 '16 at 08:43
@nrtn93 I asked for complete code, because in this line you're not setting `Name` property of the form. Thats what I mentioned. – Shaharyar Jan 27 '16 at 08:43
I set name property from the properties window of the form. – nrtn93 Jan 27 '16 at 08:45
How did you access the property window of a dynamically generated form? – Shaharyar Jan 27 '16 at 08:46

Is there any other way to access open forms in C#?

4 Answers4